I'm in bitcoin from 2012 (registered here from 2013 as you can see), most of my bitcoins doesn't have "documents". Most of exchanges I used already doesn't exists. But my bitcoins are clean.
The annoying thing about verification is when exchanges ask for unreasonable source documents that are even older than the exchange they were founded on.
I have their account and actually their verification system sucks, I signed up for level 2 with random KYC and it passed. I don't know if with these clue they can also accept any documentation. What if you kept a historical record of all the txids associated with the fund?